Compressor gurus out and about?

Bought a new skid mount compressor and having trouble with it. 13 hp. Honda and an Eaton compressor.

Unit will not idle down and not compress when there is no call for air.. Unit starts to violently surge and will lock up the engine unless I put the unloader in the start position. Having a new unloader sent out but am apprehensive as to whether it will solve the problem.